Ma family polypeptides and anti-Ma antibodies

ABSTRACT

Ma family polypeptides Ma1, Ma2, Ma3, Ma4 and Ma5 are disclosed, as are nucleic acids encoding the Ma family polypeptides, antibodies that bind to Ma family polypeptides, and methods of diagnosis of paraneoplastic syndromes, by assessing a test sample from an individual for the presence or absence, or amount, of antibodies to Ma family polypeptides.

RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.09/189,527, filed Nov. 10, 1998 now U.S. Pat. No. 6,387,639. The entire teachings of the above application is incorporated herein by reference.

GOVERNMENT SUPPORT

The invention was supported, in whole or in part, by grant NS-26064 from the National Institutes of health, and grant 08748 from the National Cancer Institute. The United States Government has certain rights in the invention.

BACKGROUND OF THE INVENTION

The concurrent existence of cancer with specific neurologic disorders, known as paraneoplastic syndromes, often requires extensive or invasive studies or is established at autopsy. Paraneoplastic symptoms usually precede the detection of the cancer, may affect any part of the nervous system, and are often more debilitating than the cancer itself. Paraneoplastic limbic encephalitis (PLE) is one of these syndromes, initially recognized in 1968 (Corsellis, J. A. N. et al., Brain 91:481–496 (1968)). The presenting symptoms of PLE are irritability, depression, seizures, severe memory deficit and dementia. These symptoms correlate with the areas of the nervous system with major pathological involvement (hippocampus, amygdala, hypothalamus, and insular and cingulate cortices) but most studies also show brainstem encephalitis (BE) and abnormalities in other areas that may or may not be clinically silent (Bakheit, A. M. O. et al., J. Neurol. Neurosurg. Psychiatry 53:1084–1088 (1990); Henson, R. A. and Urich, H., Cancer and the Nervous System, Blackwell Scientific Publications, Oxford, USA, 1989, pp. 314–345).

Due to the diversity of clinical symptoms and the frequent absence of specific markers, PLE is likely underdiagnosed. In patients with known cancer, symptoms of PLE can be attributed to other complications, including metastases to the brain, toxic and metabolic encephalopathy, infections, and side effects of cancer therapy. In about 60% of the patients, PLE precedes the detection of the tumor, complicating even more its clinical recognition (Dalmau, J. et al., Medicine 71:59–72 (1992); Alamowitch, S. et al, Brain 120:923–928 (1997)). The finding of abnormalities involving the mesial temporal lobes on MRI studies may raise the suspicion of PLE, but does not establish the diagnosis.

Some paraneoplastic syndromes affecting the nervous system are associated with antibodies that react with neuronal proteins and the causal tumor (onconeuronal antigens) (Greenlee, J. E., Ann. Neurol 12:102 (1982); Graus, F. et al., Neurology 35:538–543 (1985); Budde-Steffen, C. et al., Ann. Neurol. 23:528–531 (1988); Dalmau, J., and Posner, J. B., Semin. Oncol. 24:318–328 (1997)). Several of these antibodies are markers of specific neurologic syndromes associated with distinct types of cancer (Furneaux, H. M. et al., New Engl. J. Med. 322:1844–1851 (1990); Luque, F. A. et al., Ann. Neurol. 29:241–251 (1991); Dalmau, J. et al., Medicine 71:59–72 (1992)). The presence of some antibodies is so specific that disorders previously identified by brain biopsy, or at autopsy, can now be diagnosed serologically (Henson, R. A. et al., Brain 88:449–464 (1965); Anderson, N. E. et al., Ann. Neurol. 24:559–567 (1988); Dalmau, J. et al., Ann. Neurol. 27:544–552 (1990); Posner, J. B. (ed.), Paraneoplastic Syndromes. Neurologic Complications of Cancer, Philadelphia, FA Davis Company, pp. 353–385 (1995)). The expression of neuronal proteins by the tumor is probably a crucial step that breaks immune tolerance for otherwise normal neuronal proteins (Carpentier et al. Neurology 50:A354–355 (1998)).

To date, characteristic antineuronal antibodies have been discovered in only a few paraneoplastic disorders. Because of debilitating nature of paraneoplastic syndromes, as well as the diversity of clinical symptoms and the frequent absence of specific markers, it is critical to identify new means for diagnosing paraneoplastic syndromes.

SUMMARY OF THE INVENTION

The current invention pertains to isolated Ma family proteins, particularly Ma1 (SEQ ID NO:4), Ma2 (SEQ ID NO:7), Ma3 (SEQ ID NO:9), Ma4 (SEQ ID NO:11) and Ma5 (SEQ ID NO:13), as well as active or functional derivatives or fragments of the Ma family polypeptides. The invention also pertains to nucleic acids encoding Ma family polypeptides, as well as nucleic acid constructs comprising the nucleic acid molecules described herein operatively linked to a regulatory sequence, and to recombinant host cells comprising the nucleic acid molecules described herein operatively linked to a regulatory sequence. The invention also pertains to isolated antibodies, or antigen-binding fragments thereof, which selectively bind to Ma family polypeptides or active derivatives or fragments thereof.

The invention further pertains to methods of diagnosing a paraneoplastic syndrome in an individual, by assessing a test sample (e.g., of bodily fluid or tissue, or of antibodies isolated from a bodily fluid or tissue), for the presence, absence, or amount of antibodies that bind to a Ma family polypeptide such as Ma1 and/or Ma2. The presence of antibodies that bind to a Ma family polypeptide is indicative of the presence of a paraneoplastic syndrome; the absence of antibodies that bind to a Ma family polypeptide is indicative of the absence of a paraneoplastic syndrome. The invention additionally pertains to methods of diagnosing a neoplasm in an individual, by assessing a test sample (e.g., of bodily fluid or tissue, or of antibodies isolated from a bodily fluid or tissue), for the presence, absence, or amount of antibodies that bind to a Ma family polypeptide such as Ma1 and/or Ma2. The presence of antibodies that bind to a Ma family polypeptide is indicative of the presence of a neoplasm; the absence of antibodies that bind to a Ma family polypeptide is indicative of the absence of a neoplasm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A–1C depicts the cDNA (SEQ ID NO:3) and putative amino acid sequence (SEQ ID NO:4) for Ma1.

FIG. 2A–2B depicts the cDNA (SEQ ID NO:6) and putative amino acid sequence (SEQ ID NO:7) for Ma2.

FIGS. 3A–3B depict the homology between Ma1 cDNA (SEQ ID NO:3) and Ma2 cDNA (SEQ ID NO:6) and mouse cDNA (SEQ ID NO:14).

FIG. 4 depicts a summary of the clinical-immunological associations of antibodies to Ma1 and Ma2 to paraneoplastic syndromes.

FIG. 5A–5B depicts the cDNA (SEQ ID NO:8) and putative amino acid sequence (SEQ ID NO:9) for Ma3.

FIGS. 6A–6C depict cDNA (SEQ ID NO:10) and putative amino acid sequence (SEQ ID NO:11) for Ma4.

FIGS. 7A–7E depict cDNA (SEQ ID NO:12) and putative amino acid sequence (SEQ ID NO:13) for Ma5.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to Ma family proteins, nucleic acids that encode Ma family proteins, and the relationship of the proteins to paraneoplastic syndromes. As described herein, Applicants have identified five proteins, Ma1, Ma2, Ma3, Ma4 and Ma5, and nucleic acids encoding them. Ma1 is a 37 kilodalton protein that is expressed in brain and testis; the presence of antibodies to Ma1 (also referred to herein as “anti-Ma antibodies”) is associated with paraneoplastic syndromes, particularly those affecting the brainstem or cerebellum. Ma2 is a 40 kilodalton protein that is expressed in brain; the presence of antibodies to Ma2 (also referred to herein as “anti-Ta antibodies”) is associated particularly with testicular cancer and the paraneoplastic syndromes paraneoplastic limbic encephalitis (PLE) and brainstem encephalitis (BE). Ma3 is a 21 kilodalton protein; Ma4 is a 36 kilodalton protein; and Ma5 is a 56 kilodalton protein.

Polypeptides of the Invention

Accordingly, the invention pertains to isolated Ma family polypeptides, as well as to polypeptide products encoded by nucleotide sequences described herein. The term “polypeptide” refers to a polymer of amino acids, and not to a specific length; thus, peptides, oligopeptides and proteins are included within the definition of a polypeptide. A “Ma family polypeptide,” as used herein, refers to a polypeptide that is expressed by brain and/or testis, and that shares significant identity with Ma1, Ma2, Ma3, Ma4, and/or Ma5. A polypeptide that “shares significant identity” with is a polypeptide that has approximately 75% amino acid identity with Ma1, Ma2, Ma3, Ma4 and/or Ma5. Polypeptides exhibiting lower levels of identity are also useful and can be considered to be Ma family polypeptides, particular if they exhibit high, e.g., at least about 80%, more preferably at least about 90%, and even more preferably at least about 95%, amino acid identity with Ma1, Ma2, Ma3, Ma4 and/or Ma5 over one or more particular domains of the polypeptide. For example, polypeptides sharing high degrees of identity over domains necessary for particular activities, including antibody binding activity, are included herein.

In a preferred embodiment of the invention, the Ma family polypeptide is Ma1 (SEQ ID NO:4), Ma2 (SEQ ID NO:7), Ma3 (SEQ ID NO:9), Ma4 (SEQ ID NO:11), or Ma5 (SEQ ID NO:13). The term, “Ma family polypeptide,” also includes a polypeptide that is expressed by brain and/or testis, and that is recognized by antibodies that specifically bind to Ma1, Ma2, Ma3, Ma4, and/or Ma5. The Ma family polypeptide of the invention can be partially or substantially purified (e.g., purified to homogeneity).

The Ma family polypeptides of the present invention can be isolated or purified (e.g., to homogeneity) from recombinant cell culture by a variety of processes. A polypeptide that is “isolated” is substantially free of naturally associated components, such as by separation from the components which accompany it in its natural state. Thus, a polypeptide which is chemically synthesized, or synthesized in a cellular system different from the cell in which it naturally originates, will be substantially free of naturally associated components, and thus, is considered to be “isolated”. Methods of isolation include, but are not limited to, anion or cation exchange chromatography, ethanol precipitation, polyacrylamide gel electrophoresis, affinity chromatography and high performance liquid chromatography (HPLC). The particular method used will depend upon the properties of the polypeptide and the selection of the host cell; appropriate methods will be readily apparent to those skilled in the art.

According to the invention, the amino acid sequence of the Ma family polypeptide can be that of the naturally-occurring polypeptide (e.g., Ma1, SEQ ID NO:4, Ma2, SEQ ID NO: 7, Ma3, SEQ ID NO:9, Ma4, SEQ ID NO:11, or Ma5, SEQ ID NO:13) or can comprise alterations therein. Such alterations include conservative or non-conservative amino acid substitutions, additions and deletions of one or more amino acids; however, such alterations should preserve at least one activity of the Ma family polypeptide, i.e., the altered or mutant polypeptide should be an active or functional derivative of the naturally-occurring polypeptide. For example, the mutation(s) can preferably preserve the three dimensional configuration of an antibody binding site of the native polypeptide. Alternatively, the fragment retains other immunological activities, such as immunogenic function, as well as sharing of immunological epitopes for binding.

The presence or absence of Ma family polypeptide activity can be determined by various standard functional assays including, but not limited to, assays for binding of anti-Ma antibodies (i.e., antibodies to Ma1 or Ma2) or anti-Ta antibodies (i.e., antibodies to Ma2) to the polypeptide. Moreover, amino acids which are essential for the function of the Ma family polypeptide can be identified by methods known in the art. Particularly useful methods include identification of conserved amino acids in the superfamily of immunoglobulin genes, site-directed mutagenesis and alanine-scanning mutagenesis (for example, Cunningham and Wells, Science 244:1081–1085 (1989)), crystallization and nuclear magnetic resonance. The altered polypeptides produced by these methods can be tested for particular biologic activities, including immunogenicity and antigenicity.

Specifically, appropriate amino acid alterations can be made on the basis of several criteria, including hydrophobicity, basic or acidic character, charge, polarity, size, the presence or absence of a functional group (e.g., -SH or a glycosylation site), and aromatic character. Assignment of various amino acids to similar groups based on the properties above will be readily apparent to the skilled artisan; further appropriate amino acid changes can also be found in Bowie et al. (Science 247:1306–1310(1990)).

Other alterations of the Ma family polypeptides of the invention include, for example, glycosylations, acetylations, carboxylations, phosphorylations, ubiquitination, labelling (e.g., with radionuclides), enzymatic modifications, incorporation of analogs of an amino acid (including, e.g, natural amino acids), substituted linkages, and other modifications known in the art, both naturally and non-naturally occurring.

The invention described herein also relates to fragments of the isolated polypeptides described herein. The term “fragment” is intended to encompass a portion of a polypeptide described herein which retains one or more functions or biological activities of the isolated polypeptide, as described above (e.g., immunogenic or antigenic function). For example, the fragment can be from at least about 20 contiguous amino acids to at least about 200 contiguous amino acids, more preferably at least about 50 amino acids, even more preferably at least about 100 amino acids, even more preferably at least about 150 amino acids.

The Ma family polypeptide can also be a fusion protein comprising all or a portion of the Ma family polypeptide's amino acid sequence fused to one or more additional components. Representative fusion partners include immunoglobulins, bacterial β-galactosidase, trpE, protein A, β-lactamase, α-amylase, alcohol dehydrogenase, and yeast α mating factor. Additional components, such as radioisotopes and antigenic tags, can be selected to assist in the isolation or purification of the polypeptide or to extend the half life of the polypeptide; for example, a hexahistidine tag would permit ready purification by nickel chromatography. Furthermore, polypeptides of the present invention can be progenitors of the Ma family polypeptide; progenitors are molecules which are cleaved to form an active Ma family polypeptide.

Ma family polypeptides described herein can be isolated from naturally-occurring sources, chemically synthesized or recombinantly produced. For example, a nucleic acid molecule described herein can be used to produce a recombinant form of the encoded polypeptide via microbial or eukaryotic cellular processes. Ligating the polynucleotide sequence into a gene construct, such as an expression vector, and transforming or transfecting into hosts, either eukaryotic (yeast, avian, insect, plant or mammalian) or prokaryotic (bacterial cells), are standard procedures used in producing other well known proteins. Similar procedures, or modifications thereof, can be employed to prepare recombinant polypeptides according to the present invention by microbial means or tissue-culture technology.

Nucleic Acids of the Invention

The invention also pertains to isolated nucleic acid molecules encoding the Ma family polypeptides described above. Nucleic acid molecules of the present invention can be RNA (e.g., mRNA), or DNA, such as cDNA and genomic DNA. DNA molecules can be double-stranded or single-stranded; single stranded RNA or DNA can be either the coding (sense) strand or the non-coding (antisense) strand. Preferably, the nucleic acid molecule comprises at least about 15 nucleotides, more preferably at least about 30 nucleotides, even more preferably about 60 contiguous nucleotides, still more preferably at least about 100 contiguous nucleotides, even more preferably at least about 150 contiguous nucleotides, and even more preferably at least about contiguous 300 nucleotides. The nucleic acid molecule can be only that polynucleotide which encodes at least a fragment of the amino acid sequence of the Ma family polypeptide; alternatively, the nucleic acid molecule can include at least a fragment of the nucleic acid encoding the Ma family polypeptide along with additional non-coding sequences such as introns and non-coding 3′ and 5′ sequences (including regulatory sequences, for example). Additionally, the nucleic acid molecule can contain a marker sequence, for example, a nucleotide sequence which encodes a polypeptide, to assist in isolation or purification of the polypeptide. Such sequences include, but are not limited to, those which encode a glutathione-S-transferase (GST) fusion protein and those which encode a hemagglutinin A (HA) peptide marker from influenza. In a preferred embodiment, the nucleic acid molecule has the sequence encoding Ma1 (SEQ ID NO:3); the sequence encoding Ma2 (SEQ ID NO:6); the sequence encoding Ma3 (SEQ ID NO:8); the sequence encoding Ma4 (SEQ ID NO:10); or the sequence encoding Ma5 (SEQ ID NO:12).

As used herein, an “isolated” or “substantially pure” nucleic acid molecule is intended to mean a nucleotide sequence which is not flanked by nucleotide sequences which normally (in nature) flank the gene or nucleotide sequence (as in genomic sequences) and/or has been completely or partially purified from other transcribed sequences (as in a cDNA or RNA library). Thus, an isolated nucleotide sequence can include a nucleotide sequence which is synthesized chemically or by recombinant means. Thus, recombinant DNA contained in a vector are included in the definition of “isolated” as used herein. Also, isolated nucleotide sequences include recombinant DNA molecules in heterologous host cells, as well as partially or substantially purified DNA molecules in solution. In vivo and in vitro RNA transcripts of the DNA molecules of the present invention are also encompassed by “isolated” nucleotide sequences. Such isolated nucleotide sequences are useful in the manufacture of the encoded protein, as probes for isolating homologous sequences (e.g., from other mammalian species), for gene mapping (e.g., by in situ hybridization with chromosomes), or for detecting expression of the Ma family polypeptide in tissue (e.g., human tissue), such as by Northern blot analysis.

The present invention also pertains to nucleic acid molecules which are not necessarily found in nature but which encode the Ma family polypeptide. Thus, DNA molecules which comprise a sequence that is different from the naturally-occurring nucleotide sequence but which, due to the degeneracy of the genetic code, encode the Ma family polypeptide of the present invention are the subject of this invention (e.g., a nucleic acid molecule that encodes SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, or SEQ ID NO:13). The invention also encompasses variations of the nucleotide sequences of the invention, such as those encoding portions, analogues or derivatives of the Ma family polypeptide. Such variations can be naturally-occurring, such as in the case of allelic variation, or non-naturally-occurring, such as those induced by various mutagens and mutagenic processes. Intended variations include, but are not limited to, addition, deletion and substitution of one or more nucleotides which can result in conservative or non-conservative amino acid changes, including additions and deletions. Preferably, the nucleotide or amino acid variations are silent or conserved; that is, they do not alter the characteristics or activity of the Ma family polypeptide.

Other alterations of the nucleic acid molecules of the invention can include, for example, labelling, methylation, internucleotide modifications such as uncharged linkages (e.g., methyl phosphonates, phosphotriesters, phosphoamidates, carbamates), charged linkages (e.g., phosphorothioates, phosphorodithioates), pendent moieties (e.g., polypeptides), intercalators (e.g., acridine, psoralen), chelators, alkylators, and modified linkages (e.g., alpha anomeric nucleic acids). Also included are synthetic molecules that mimic nucleic acid molecules in the ability to bind to a designated sequences via hydrogen bonding and other chemical interactions. Such molecules include, for example, those in which peptide linkages substitute for phosphate linkages in the backbone of the molecule.

The invention also relates to fragments of the isolated nucleic acid molecules described herein. The term “fragment” is intended to encompass a portion of a nucleic acid sequence described herein, such as a portion which encodes a fragment of a Ma family polypeptide as described above. For example, a fragment can be a portion of a nucleic acid which is from at least about 15 contiguous nucleotides to at least about 300 contiguous nucleotides or longer in length. One or more introns can also be present. Such fragments are useful as probes, e.g., for diagnostic methods and also as primers or probes. Particularly preferred primers and probes selectively hybridize to the nucleic acid molecule encoding the Ma family polypeptides described herein. For example, fragments which encode antigenic regions of the Ma family polypeptides described herein are useful.

The invention also pertains to nucleic acid molecules which hybridize under medium, and, more preferably, high, stringency hybridization conditions (e.g., for selective hybridization) to a portion of a nucleic acid molecule described herein. Appropriate stringency conditions are known to those skilled in the art or can be found in standard texts such as Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1998), 6.3.1–6.3.6. Such hybridizable nucleic acid molecules are useful as probes and primers for diagnostic applications. For example, high stringency hybridization conditions for Southern blotting include conditions with a temperature that is from about 12–20° C. below the calculated Tm (Tm is based upon the nucleotide sequence of the probe and can be calculated for each probe); alternatively, high stringency conditions include low salt conditions.

Accordingly, the invention pertains to nucleic acid molecules that have a substantial identity with the nucleotide sequences described herein. Particularly preferred are nucleic acid molecules which have at least about 60%, more preferably at least about 85%, even more preferably at least about 95%, and still more preferably at least about 99% identity with nucleotide sequences described herein. Also particularly preferred in this instance are nucleic acid molecules encoding polypeptides having at least one activity of the Ma family polypeptides described herein. For example, preferred nucleic acid molecules encoding a polypeptide having the same or similar immunogenic or antigenic properties as the Ma family polypeptide are within the scope of the invention. Nucleic acid molecules which have lower overall homologies are also included herein, provided that they have substantial identity over fragments of the polypeptide. For example, the Ma family polypeptides each contain segments (ranging from approximately 15 nucleotides to approximately 100 nucleotides, with segments up to 120 and to 360 nucleotides) having substantial homology (ranging from at least 60% to at least 95%) with one another. Ma1 and Ma2 share substantial identity, ranging from 60% to 76.5%, over five separate segments: nucleotides 11–38 of Ma2 and 678–705 of Ma1 (71.4% homology); nucleotides 78–109 of Ma2 and 745–776 of Ma1 (68.8% homology); nucleotides 150–165 of Ma2 and 814–829 of Ma1 (60% homology); nucleotides 184–200 of Ma2 and 846–864 of Ma1 (76.5% homology); and nucleotides 246–341 of Ma2 and 910–1005 of Ma1 (74% homology). The substantial homology over several segments indicates that the encoded polypeptides are closely related. Thus, nucleic acid molecules which similarly have lower overall homology to a Ma family polypeptide, but which have substantial homology to one or more regions of the Ma family polypeptide, are encompassed by the invention.

The invention also provides expression vectors containing a nucleotide sequence encoding a Ma family polypeptide or active derivative or fragment thereof, operably linked to at least one regulatory sequence. Many such vectors are commercially available, and other suitable vectors can be readily prepared by the skilled artisan. “Operably linked” is intended to meant that the nucleotide sequence is linked to a regulatory sequence in a manner which allows expression of the nucleotide sequence. Regulatory sequences are art-recognized and are selected to produce a Ma family polypeptide or active derivative thereof. Accordingly, the term “regulatory sequence” includes promoters, enhancers, and other expression control elements which are described in Goeddel, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. (1990). For example, the native regulatory sequences or regulatory sequences native to the transformed host cell can be employed. It should be understood that the design of the expression vector may depend on such factors as the choice of the host cell to be transformed and/or the type of protein desired to be expressed. For instance, the polypeptides encoded by the nucleic acid molecules of the present invention can be produced by ligating the cloned gene, or a portion thereof, into a vector suitable for expression in either prokaryotic cells, eukaryotic cells or both (see, for example, Broach, et al., Experimental Manipulation of Gene Expression, ed. M. Inouye (Academic Press, 1983) p. 83; Molecular Cloning: A Laboratory Manual, 2nd Ed., ed. Sambrook et al. (Cold Spring Harbor Laboratory Press, 1989) Chapters 16 and 17). Typically, expression constructs will contain one or more selectable markers, including, but not limited to, the gene that encodes dihydrofolate reductase and the genes that confer resistance to neomycin, tetracycline, ampicillin, chloramphenicol, kanamycin and streptomycin resistance. Vectors can also include, for example, an autonomously replicating sequence (ARS), expression control sequences, ribosome-binding sites, RNA splice sites, polyadenylation sites, transcriptional terminator sequences, secretion signals and MRNA stabilizing sequences.

Prokaryotic and eukaryotic host cells transformed by the described vectors are also provided by this invention. For instance, cells which can be transformed with the vectors of the present invention include, but are not limited to, bacterial cells such as E. coli (e.g., E. coli K12 strains), Streptomyces, Pseudomonas, Serratia marcescens and Salmonella typhimurium, insect cells (baculovirus), including Drosophila, fungal cells, such as yeast cells, plant cells and mammalian cells, such as thymocytes, Chinese hamster ovary cells (CHO), and COS cells. The host cells can be transformed by the described vectors by various methods (e.g., electroporation, transfection using calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection, infection where the vector is an infectious agent such as a retroviral genome, and other methods), depending on the type of cellular host.

The nucleic acid molecules of the present invention can be produced, for example, by replication in a suitable host cell, as described above. Alternatively, the nucleic acid molecules can also be produced by chemical synthesis.

Antibodies of the Invention

The present invention also relates to isolated antibodies, or antigen-binding fragments, which bind to a Ma family polypeptide (or polypeptides). For instance, polyclonal and monoclonal antibodies, including non-human and human antibodies, humanized antibodies, chimeric antibodies and antigen-binding fragments thereof (Current Protocols in Immunology, John Wiley & Sons, N.Y. (1994); EP Application 173,494 (Morrison); International Patent Application WO86/01533 (Neuberger); and U.S. Pat. No. 5,225,539 (Winters)) which bind to the described Ma family polypeptides are within the scope of the invention. A mammal, such as a mouse, rat, hamster or rabbit, can be immunized with an immunogenic form of the Ma family polypeptide (e.g., the protein or a peptide comprising an antigenic fragment of the protein which is capable of eliciting an antibody response). Techniques for conferring immunogenicity on a protein or peptide include conjugation to carriers or other techniques well known in the art. The protein or polypeptide can be administered in the presence of an adjuvant. The progress of immunization can be monitored by detection of antibody titers in plasma or serum. Standard ELISA or other immunoassays can be used with the immunogen as antigen to assess the levels of antibody.

Following immunization, anti-peptide antisera can be obtained, and if desired, polyclonal antibodies can be isolated from the serum. Monoclonal antibodies can also be produced by standard techniques which are well known in the art (Kohler and Milstein, Nature 256:495–497 (1975); Kozbar et al., Immunology Today 4:72 (1983); and Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77–96 (1985)). The term “antibody” as used herein is intended to include fragments thereof, such as Fab and F(ab)₂′. Such antibodies, in conjunction with a label, such as a radioactive label, can be used to assay for the presence of the expressed protein in a cell from, e.g., a tissue sample. Such antibodies can also be used in an immunoabsorption process, such as an ELISA, to isolate the Ma family polypeptide. Tissue samples which can be assayed include primate, particularly human, tissues, e.g., differentiated and nondifferentiated cells. Examples include brain and testis.

Methods of Diagnosis of the Invention

Because of the relationship between the Ma family polypeptides Ma1 and Ma2 with paraneoplastic syndromes, methods are now available for diagnosing the presence or absence of a paraneoplastic syndrome in an individual, by assessing a test sample from an individual for the presence or absence of antibodies to Ma family polypeptide(s). The presence of antibodies to a Ma family polypeptide is indicative of the presence of a paraneoplastic syndrome; the absence of antibodies to a Ma family polypeptide is indicative of the absence of the paraneoplastic syndrome. The term, “paraneoplastic syndrome,” as used herein, refers to a neurologic disorder that is associated with the presence of a neoplasm (cancer), but is not due to direct invasion of the nervous system by the neoplasm or due to other complications such as side effects of treatment, infections, metabolic and nutritional deficits and cerebrovascular disorders. In a preferred embodiment, the presence of antibodies that bind to the Ma family polypeptide, Ma1, is indicative of a paraneoplastic syndrome. In another preferred embodiment, the presence of antibodies that bind to the Ma family polypeptide, Ma2, is indicative of a paraneoplastic syndrome. In a particularly preferred embodiment, the presence of antibodies that bind to Ma2 is indicative of the paraneoplastic syndrome(s), paraneoplastic limbic encephalitis and/or brainstem encephalitis. The presence of antibodies that bind to more than one Ma family polypeptide (e.g., to both Ma1 and Ma2) is also indicative of the presence of a paraneoplastic syndrome.

In addition, methods are now available for diagnosing the presence or absence of a neoplasm in an individual, by assessing a test sample from an individual for the presence or absence of antibodies to Ma family polypeptide(s). Because paraneoplastic syndromes often occur prior to discovery of the underlying neoplasm, these methods facilitate identification of the presence of a neoplasm by identifying a neurologic disorder as a paraneoplastic syndrome. In addition, antibodies to a Ma family polypeptide(s) may be present in an individual (e.g., at low levels) in the absence of paraneoplastic pathology (i.e., in the absence of a paraneoplastic syndrome); the methods of the invention facilitate identification of the presence of a neoplasm in these individuals as well. The presence of antibodies to a Ma family polypeptide is indicative of the presence of a paraneoplastic syndrome, and therefore is indicative of the presence of a neoplasm. In a preferred embodiment, the presence of antibodies that bind to the Ma family polypeptide Ma1 (e.g., anti-Ma antibodies), is indicative of the presence of a neoplasm. In a particularly preferred embodiment, the neoplasm is breast cancer, colon cancer, lung cancer, testicular cancer, a germ cell tumor or parotid gland cancer. In another preferred embodiment, the presence of antibodies that bind to the Ma family polypeptide Ma2 (e.g., anti-Ta antibodies) is indicative of the presence of a testicular neoplasm and/or a germ cell tumor. The absence of antibodies to a Ma family polypeptide is indicative of the absence of a paraneoplastic syndrome, and therefore is indicative of the absence of a neoplasm.

In the methods of the invention, a test sample from an individual, such as an individual who is suspected of having a paraneoplastic syndrome, is used. The test sample can also be from an individual who is suspected of having a cancer, but who does not demonstrate a paraneoplastic syndrome. The test sample can comprise blood, serum, cerebrospinal fluid, urine, nasal secretion, saliva, or any other bodily fluid or tissue. Alternatively, the test sample can comprise antibodies isolated from a sample of bodily fluid or tissue from the individual. If the sample is isolated antibodies, the isolated antibodies can include a single type of antibody (e.g., IgA, IgD, IgE, IgG or IgM antibodies), or can include all types of antibodies; alternatively, one or more types of antibodies (e.g., IgM antibodies, IgG antibodies, or IgM and IgG antibodies) can be isolated. In a preferred embodiment, the test sample is a serum sample or a cerebrospinal fluid sample from the individual.

The test sample is assessed for the presence or absence of antibodies that bind to a Ma family polypeptide (or to more than one Ma family polypeptide). In one embodiment of the invention, one or more of the Ma family polypeptides described above can be used to detect the presence of antibodies to the Ma family polypeptide. In these methods, a Ma family polypeptide sample is used. The term, “Ma family polypeptide sample,” as used herein, can be a sample containing a Ma family polypeptide, or active derivative or fragment thereof, as described above. The Ma family polypeptide sample can also contain more than one Ma family polypeptide or active derivative or fragment (e.g., a Ma family polypeptide sample containing Ma1 and Ma2). In a preferred embodiment, the Ma family polypeptide sample comprises Ma1 and/or Ma2. The Ma family polypeptide sample can be a sample of isolated Ma family polypeptide(s); alternatively, the Ma family polypeptide sample can be a sample that comprises Ma family polypeptide(s) (e.g., slice(s) of tissue, such as neuronal tissue from human brain or rat brain, or another tissue known to contain the Ma family polypeptide(s), or a homogenate of tissue(s) known to contain the Ma family polypeptide(s)).

The Ma family polypeptide sample is contacted with the test sample from an individual. Contact of the Ma family polypeptide sample with the test sample from the individual results in a “contacted sample,” which is a mixture of the Ma family polypeptide sample and the test sample. The contacted sample is maintained under appropriate conditions to allow binding of antibody to Ma family polypeptide, if such antibody is present in the sample, to the Ma family polypeptide. The terms, “anti-Ma family polypeptide antibody” or “anti-Ma family polypeptide autoantibody”, as used herein, refer to antibody that specifically binds to a Ma family polypeptide as described above. The presence or absence of anti-Ma family polypeptide antibody is then assessed.

In one embodiment of the invention, the amount of anti-Ma family polypeptide antibodies, if any, that have bound to the Ma family polypeptide in the contacted sample, is compared to a reference amount. The term, “reference amount,” as used herein, refers to an amount of anti-Ma family polypeptide antibodies that correlates with a diagnosis of an paraneoplastic syndrome or of a neoplasm. A reference amount can be determined, for example, by comparing amounts of anti-Ma family polypeptide antibodies in contacted samples from individuals known to have a paraneoplastic syndrome (e.g., a “positive control sample”), with amounts of anti-Ma family polypeptide antibodies in contacted samples from individuals known not to have a paraneoplastic syndrome (e.g., a “negative control sample” as described below), and determining what amount of antibody correlates with disease. The reference amount can be determined by determining the amounts of anti-Ma family polypeptide antibodies in positive and/or negative control samples concurrently with determining the amount of anti-Ma family polypeptide antibodies in the contacted sample; alternatively, the reference amount can be a historically determined amount (i.e., an amount determined prior to determining the amount of anti-Ma family polypeptide antibodies in the contacted sample). For example, in one embodiment, a “reference amount” can be an amount of anti-Ma family polypeptide antibody in the test sample that statistically is significantly greater than the amount of anti-Ma family polypeptide antibody in comparable control sample(s). In one embodiment, an amount of anti-Ma family polypeptide in the test sample is statistically significant when it is two standard deviations greater than the amount of anti-Ma family polypeptide antibody in comparable control samples.

The amount of different types of antibodies (i.e., a sum including the amount of more than one type of antibody) can be compared to the reference amount; alternatively, the amount of one particular type of antibody (e.g., the amount of IgA, IgD, IgE, IgM or IgG antibody) can be compared to the reference amount. In a preferred embodiment, the antibody is IgG antibody. The reference amount is an amount of the same type of antibody as the antibody assessed in the contacted sample: for example, if the sum of the amount of different types of antibodies (i.e., including more than one type of antibody) for the contacted sample is compared to the reference amount, the sum of the amount of those types of antibodies is also used for the reference amount. If the amount of one particular type of antibody (e.g., the amount of IgM or IgG antibodies) in the contacted sample is compared with the reference amount, the amount of that type of antibodies is also used for the reference amount.

In one embodiment, the presence of an amount that is equal to, or greater than, the reference amount correlates with a diagnosis of (is indicative of the presence of) paraneoplastic syndrome. Similarly, the presence of an amount that is equal to, or greater than, the reference amount correlates with the presence of a neoplasm. An amount that is less than the reference amount correlates with (is indicative of) an absence of paraneoplastic syndrome. Similarly, the presence of an amount that is less than the reference amount correlates with the absence of a neoplasm.

In another embodiment of the invention, the contacted sample is assayed to determine the amount of anti-Ma family polypeptide antibodies, if any, that have bound to the Ma family polypeptide. The assay can determine an amount that is the sum of the amount of different types of antibodies (i.e.,including more than one type of antibody); alternatively, the assay can determine the amount of one particular type of antibody (e.g., the amount of IgA, IgD, IgE, IgM or IgG antibody). In a preferred embodiment, the contacted sample is assayed to determine the amount of IgM or IgG antibody.

The amount of anti-Ma family polypeptide antibody in the contacted sample is compared with the amount of anti-Ma family polypeptide antibody in at least one comparable negative control sample (i.e., a sample from an individual who is not afflicted by a paraneoplastic syndrome). The negative control sample can be a sample from any individual who is not afflicted with a paraneoplastic syndrome. It is not necessary that the negative control sample be from an individual who is free of disease: for example, the negative control sample can be a sample from an individual who has cancer but no paraneoplastic syndrome. A “comparable” negative control sample is a sample of the same type of body fluid or tissue as the test sample; alternatively, if the test sample is antibodies isolated from a sample of fluid or tissue, the comparable negative control sample is a sample of antibodies isolated from the same type of bodily fluid or tissue. More than one control sample can be used. The assay of the negative control sample determines the same type of antibody as the assay of the contacted sample: for example, if the sum of the amount of different types of antibodies (i.e., including more than one type of antibody) is detected for the contacted sample, the sum of the amount of those types of antibodies is also determined for the negative control sample. If the assay determines the amount of one particular type of antibody (e.g., the amount of IgM or IgG antibodies) in the contacted sample, the amount of that type of antibodies is also determined for the negative control sample. In a preferred embodiment, more than one control sample can be used.

The amount of antibody, or the presence or absence of antibody, can be determined by a variety of methods using standard techniques, including enzyme-linked immunosorbent assay (ELISA) or other solid phase immunoassays, radioimmunoassay, nephelometry, electrophoresis, immunofluorescence, Western blot (immunoblot), or other methods (see Ausubel, F. M. et al., eds., Current Protocols in Molecular Biology, John Wiley & Sons, including supplements through 1997, especially units 11.2 (ELISA) and 11.16 (Determination of Specific Antibody Titer)). In a preferred embodiment, the titer is determined by ELISA; in another preferred embodiment, the amount (or presence or absence) of antibody is determined by Western blot. For example, the amount (or presence or absence of antibody) can be determined by using section(s) of neuronal tissue, such as human and/or rat brain, as the Ma family polypeptide sample; the sections are incubated with the test samples, and then presence or absence, or amount, of anti-Ma family polypeptide antibodies, can be assessed by an appropriate method, such as by a detector antibody or indirect immunofluorescence. In another example, the amount (or presence or absence of antibody) can be determined by using homogenized neuronal tissue, and separating the proteins on a Western blot; the blot is then incubated with the test samples, and then presence or absence, or amount, of anti-Ma family polypeptide antibodies, can be assessed by an appropriate method, such as by a detector antibody or indirect immunofluorescence. The presence of a protein band at an appropriate weight (e.g., at the molecular weight of the Ma family polypeptide) is indicative of the presence of anti-Ma family polypeptide antibodies. In a particularly preferred embodiment, the Ma family polypeptide is attached to a solid support. Typically, the amount of antibody that binds to the Ma family polypeptide sample can be determined using a detector antibody that binds to the anti-Ma family polypeptide antibody.

The presence of an amount of anti-Ma family polypeptide antibody in the test sample that is significantly greater than the amount of anti-Ma family polypeptide antibody in a comparable control sample(s), correlates with the presence of a paraneoplastic syndrome. The presence of an amount of anti-Ma family polypeptide antibody in the test sample that is not significantly greater than the amount of anti-Ma family polypeptide antibody in a comparable control sample(s), correlates with an absence of a paraneoplastic syndrome. For example, if immunohistochemistry is used, the presence of greater reactivity in serum of a patient diluted 1:500, than in a control sample(s), correlates with a diagnosis of paraneoplastic syndrome; the absence of visible reactivity in serum of a patient diluted 1:500, is indicative of the absence of paraneoplastic syndrome. In another embodiment, if Western blotting is used, the presence of greater reactivity in serum of a patient diluted 1:1,000, than in a control sample(s), correlates with a diagnosis of paraneoplastic syndrome; the absence of visible reactivity in serum of a patient diluted 1:1,000, correlates with the absence of paraneoplastic syndrome. Similarly, the presence of an amount of anti-Ma family polypeptide antibody in the test sample that is significantly greater than the amount of anti-Ma family polypeptide antibody in a comparable control sample(s), correlates with the presence of a neoplasm. The presence of an amount of anti-Ma family polypeptide antibody in the test sample that is not significantly greater than the amount of anti-Ma family polypeptide antibody in a comparable control sample(s), correlates with the absence of a neoplasm.

The present invention also includes kits to be used in methods of the invention. Kits can include the following components: (1) a Ma family polypeptide sample; and, optionally, (2) labeled detector antibody that binds to antibody, preferably to the anti-Ma family polypeptide antibody. Detector antibody can comprise an antibody bound to a detectable agent, such as an enzyme, radioactive molecule, or fluorescent agent. If the detector antibody is bound to an enzyme that reacts with an added substrate to yield a colored product, such as horseradish peroxidase, the kit can also include the substrate. The Ma family polypeptide sample in the kit can be adhered to a solid support.

The following Examples are offered for the purpose of illustrating the present invention and are not to be construed to limit the scope of this invention. The teachings of all references cited herein are hereby incorporated herein by reference.

EXAMPLES Example 1 Identification of Ma1, A Neuronal and Testis Specific Protein that is Recognized by the Serum of Patients with Paraneoplastic Neurologic Disorders

The serum of patients with suspected paraneoplastic syndromes was examined for antineuronal antibodies. A novel antineuronal antibody (called anti-Ma) was identified in the serum of four patients with paraneoplastic neurologic syndromes. Identification of the expression of the target antigens in rat and normal human tissues and tumors, and cloning of Ma1, a novel neuronal and testis specific protein recognized by anti-Ma sera, were performed as described below.

A. Material and Methods

-   -   Patients, sera and tissues

The sera (or cerebrospinal fluid when available) from 1,705 patients that were sent to be screened for paraneoplastic antineuronal antibodies were used in a study. At the time that these sera were collected, 984 of the patients had a cancer diagnosis. Sera used as controls included sera from 52 normal individuals; sera from 96 patients with well characterized paraneoplastic syndromes (44 anti-Hu related encephalomyelitis and sensory neuronopathy; 17 anti-Yo related cerebellar degeneration; 11 Lambert-Eaton myasthenic syndrome with P/Q-type voltage gated calcium-channel antibodies [VGCC]; 2 anti-Ri related cerebellar ataxia and opsoclonus; 6 anti-Tr related cerebellar dysfunction; 5 myasthenia gravis associated with thymoma; and 11 opsoclonus associated with neuroblastoma); sera from 179 patients with cancer (44 testicular, 10 colon, 10 ovarian, 40 lung, 22 breast, 20 brain tumors, and 33 neuroblastomas) but without paraneoplastic neurologic syndromes; sera from 6 patients with amyotrophic lateral sclerosis without cancer; and sera from 4 patients with myasthenia gravis without thymoma.

Sera were kept frozen at −70° C. Human nervous system and systemic tissues were obtained from autopsy or biopsy studies of neurologically normal individuals. Fifty three cancer tissues (15 colon, 5 breast, 5 bladder, 3 parotid, 5 neuroblastomas, 5 non-small cell lung cancer, and 15 testicular germ cell tumors) from patients without paraneoplastic symptoms and 13 from patients with antibody associated paraneoplastic disorders (4 ovary, 4 lung, 2 uterus, 1 bladder, 1 larynx and 1 chondrosarcoma) were provided by the Tumor Procurement Service at Memorial Sloan-Kettering Cancer Center.

Wistar rats were anesthetized and perfused with saline, followed by removal of brain and other tissues. Samples of human and rat tissues were kept at −70° C.; other samples from the same tissues were embedded in Optimal Cutting Temperature medium (OCT, Miles Inc, USA) and frozen in isopentane chilled by liquid nitrogen.

For studies of human tumors and immunohistochemical competition assays, the IgG from patients' sera was isolated using a protein-G sepharose column (Sigma, St Louis, Mo.) followed by labeling with biotin (Fumeaux, H. M. et al., New Engl. J. Med. 322:1844–1851 (1990)).

For Western blot analysis, human tissues were homogenized in 0.1% Nonidet P-40 and protease inhibitors: PMSF (50 μg/ml), aprotinin (1 μg/ml), pepstatin (1 μg/ml), and leupeptine (1 μg/ml) (all from Sigma).

-   -   Immunohistochemistry

Seven micron-thick frozen sections of rat and human brain and cerebellum were fixed in formalin, 100% methanol, or cold acetone (4° C.) and sequentially incubated with 0.3% hydrogen peroxide in phosphate buffered saline (PBS) for 10 minutes, 10% normal goat serum for 20 minutes, the patient's serum diluted at 1:500 for 2 hours, biotinylated goat anti-human IgG (Vector, Burlingame, Calif.) diluted 1:2,000, for 30 minutes, and the avidin biotin peroxidase complex (Vector) for 30 minutes. The reaction was developed with 0.05% diaminobenzidine tetrahydrochloride (Sigma) with 0.01% hydrogen peroxide and 0.5% Triton X-100 in PBS. Patient's serum and secondary antibody were diluted in 10% normal goat serum in PBS. Between steps, slides were washed with PBS.

To avoid reactivity with endogenous IgG, all immunohistochemical studies on systemic human tissues and tumors utilized biotinylated IgG isolated from the patients' sera. All steps were done as above except that preincubation of the sections with 10% normal human serum was used to block nonspecific IgG binding, and no secondary antibody was used.

For competition assays, tissue sections were preincubated with the serum of one of the patients (diluted 1:5) for one hour, followed by incubation with biotinylated IgG isolated from the serum of another patient (diluted 1:25). Tissues preincubated with normal human serum or serum from patients with other antineuronal antibodies (diluted 1:5) served as controls. Sera were considered to compete for the same epitopes, when the reactivity of the biotinylated IgG of one patient was abrogated by preincubation of the tissue with serum from another patient.

-   -   Screening of a cerebellar cDNA expression library

A λ ZAP human cerebellar library (Stratagene, La Jolla, Calif.) was screened at a density of 5×10⁴ pfu/150 mm plate. After a 3 hour incubation at 42° C., plates were overlaid with filters soaked in 10 mmol/L isopropyl β-D-thiogalactopyranoside (IPTG) and incubated for 4 hours at 37° C. Plates were then cooled for 20 minutes at 4° C., and filters were removed, blocked with 1% bovine serum albumin (BSA) for 12 hours at 4° C., and incubated for 3 hours with serum (diluted 1:1,000) from a patient with paraneoplastic brainstem and cerebellar dysfunction. After washing with Tween-20, filters were incubated with I¹²⁵ protein A (0.1 μCi/mL) for 1 hour, washed, dried and exposed to XAR5 film for 24 hours at −70° C. Clones giving positive results were purified by several rounds of antibody screening until a yield of 100% positive plaques was obtained. Phage clones were subcloned in pBluescript using the in vivo excision phage rescue protocol (Stratagene).

-   -   DNA Sequencing

Sequence analysis was performed with an automated DNA sequencer (ABI 377) using the dye terminator fluorescence method (Lee, L. G. et al., Nucl. Acids Res. 20:2471–2483 (1992)). Double-stranded DNA was purified using the Qiagen plasmid midi-prep system (Qiagen, Santa Clarita, Calif.) and sequenced on both strands. Internal oligonucleotide primers, as well as SK and KS primers, were used.

-   -   Western blot analysis

Fusion protein and E. coli protein extracts were obtained by growing an individual colony to an optical density of 0.6 and inducing with 10 mmol/L IPTG for 3 hours at 37° C. Cells were isolated by centrifugation and lysed by resuspension in 0.1% NP-40 and 2% sodium dodecyl sulfate (SDS) in PBS.

Lysates of fusion proteins, or proteins extracted from human and rat tissues, were resolved by 10% SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose (Towbin, H. et al., Proc. Natl. Acad. Sci. USA 76:4350–4 (1979)). After blocking with 5% dry Carnation™ milk, nitrocellulose strips were sequentially incubated with the patient's serum (1:1,000 dilution) for 2 hours, and sheep anti-human horseradish peroxidase-labeled IgG (Amersham, Arlington Heights, Ill.) diluted 1:20,000, for one hour. Strips were then immersed in an enhanced chemiluminescence solution (Amersham, Arlington, Ill.) for 1 minute, and exposed to Kodak XAR5 film (Sigma). Between steps, strips were washed with 0.05% Tween-20 in PBS. All incubations were done at room temperature (RT).

-   -   Northern blot analysis

Sequence specific oligonucleotide probes were end-labeled with [γ-³²P] ATP using T4 polynucleotide kinase. As probe for Ma1, the following oligonucleotide was used: 5′-GAAACCCAAGGACACGGG-3′ (SEQ ID NO:1; cDNA base pairs 647–630), and as probe for β-actin, the following oligonucleotide was used: 5′-GTCTTTGCGGATGTCCACG-3′ (SEQ ID NO:2). Labeled probes were extracted with phenol chloroform and purified over a G-25 sephadex column. Probes (1×10⁷ cpm/mL) were hybridized to “Human Multiple Tissue Northern Blots I and II” (Clontech, Palo Alto, Calif.) overnight at 42° C. in Rapid Hyb buffer (Amersham). Blots were washed for 15 minutes at RT in 5×SSC (20×=NaCl 3M and Na₃Citrate 0.3M, pH 7.0), 0.1% SDS; at 42° C. in 1×SSC, 0.1% SDS; and at 42° C. in 0.1×SSC, 0.1% SDS. After hybridization with the Ma1 probe, blots were stripped by boiling in 0.5% SDS for 10 minutes and hybridized with β-actin probe. For visualization, blots were exposed to XAR film for 72 hours at −80° C.

B. Results

-   -   Clinical and Pathological Findings

The study of 1,705 sera resulted in the identification of 4 patients who harbored a novel antineuronal antibody, that is called anti-Ma. The clinical information of these patients is summarized in Table 1.

TABLE 1 Clinical Features of 4 Patients with Paraneoplastic Syndromes Time from Tumor, Stage Patient, PNS to tumor First neurological Paraneoplastic (Expression of Ma Neurological Sex, age diagnosis symptom(s) syndrome Ags) treatment Outcome Autopsy Patient 1  6 months Gait difficulty, Pancerebellar Parotid, limited. IVIg, Stable, 2 years — F, 63 poor arm syndrome (unable to (Ma Ag+) Protein A after first coordination, walk), dysphagia, column symptom slurred speech, oscillopsia, absent head tremor reflexes (both knees and right ankle). Vibratory loss in toes. Patient 2 Preceded (? Ataxia of Cerebellar Breast, extensive. None Dead, from Severe loss of F, 63 Months) extremities dysfunction (Ma Ag+) systemic Purkinje cells & cancer complica-tions Bergmann gliosis. recurrence Inflammatory infiltrates of T cells in the cerebellar white matter. Patient 3 1 year Dysphagia Dysphagia, mild Large-cell cancer Tumor Lost to follow- — M, 58 proximal weakness, of the lung, resection up absent ankle limited. reflexes, decreased (Ma Ag, not vibratory and studied) temperature sensation in feet, impotence. Patient 4 11 months Diplopia, Abolished vertical Colon, limited. IVIg, Plasma Dead, from Neuronal loss & F, 58 unsteadiness, eye movements; (Ma Ag+) exchange, neurologic gliosis involving: pseudobulbar limited adduction of Prednisone disease brainstem, Purkinje affect left eye, dysarthria, cells, the dentate myokymia and nucleus of the decreased sensation cerebellum. T-cell on left side of the infiltrates & face, wide-base gait. microglial nodules: Mild cognitive brainstem (mainly deficit. medulla), cerebellar white matter, hypothalamus, substantia innominata PNS: Paraneoplastic symptoms; Ma Ags: Ma antigens; IVIg: Intravenous immunoglobulin

Neurologic symptoms preceded the diagnosis of the tumor in 3 patients, and preceded recurrence of a breast cancer diagnosed 6 years earlier in 1 patient. Three patients had symptoms of cerebellar and/or brainstem involvement; the associated cancers were breast, parotid, and colon. Another patient with a history of mild dysphagia, proximal weakness and sexual impotence for one year, underwent mediastinoscopy and biopsy of a large cell carcinoma of the right bronchus; after anesthesia he developed respiratory muscle weakness. Neurophysiological studies and serological test (P/Q-type voltage gated calcium channel antibodies) for the Lambert-Eaton myasthenic syndrome, were negative. This patient was lost to follow-up and it is not known if he developed other neurological symptoms.

Among the three patients with available clinical information, two received immunomodulatory treatments (intravenous immunoglobulin, protein A column immunoabsorption, plasma exchange), but none improved the neurologic deficits. One patient is alive and two are dead, one from multiple systemic problems (peritoneal carcinomatosis, sepsis, coagulopathy), the other from progressive brainstem dysfunction.

At autopsy, one patient had extensive systemic metastases of breast cancer, and micronodular cirrhosis. No metastases were identified in the nervous system (spinal cord not examined). There was almost complete absence of Purkinje cells in the cerebellum, associated with Bergmann gliosis, and mild inflammatory infiltrates in the deep cerebellar white matter. Neuritic plaques were identified in cortex (mainly in the occipital lobe), but no other abnormalities were found in cerebral cortex, amygdala and brainstem. This patient had no history suggesting Alzheimer's disease.

The autopsy of the other patient was restricted to brain, and the possibility of clinically undetected systemic metastases could not be ruled out. The tectal and tegmental regions of the midbrain, pontine tegmentum, and medulla showed extensive perivascular and interstitial inflammatory infiltrates with microglial nodules. Severe neuronal loss and gliosis were found in the inferior olivary nucleus and surrounding tissue. There was also focal loss of Purkinje cells and of neurons of the dentate nucleus, with Bergmann gliosis. Inflammatory infiltrates were found in the deep cerebellar white matter. Milder perivascular and interstitial lymphocytic infiltrates were observed in the hypothalamus and substantia innominata.

In both patients, immunohistochemical analysis of the inflammatory infiltrates with markers for B (CD20) cells, T (CD3) cells, and subtypes of T cells (CD4 and CD8), demonstrated that most (>90%) of the cells were T-lymphocytes, mainly CD8+(>75% of T-cells).

-   -   Laboratory Findings     -   Anti-Ma antibodies specifically react with normal brain and         testis

The sera of the above 4 patients reacted with all neurons of the central and peripheral nervous system, including sympathetic and dorsal root ganglia, and myenteric plexus, in a characteristic pattern. Anti-Ma antibodies reacted mainly within subnuclear elements (nuclei and nucleoli) of neurons, and to a lesser degree with the cytoplasm. Non-neuronal cells did not react. Reactivity was not affected by formalin, methanol, or acetone fixation, but it was better preserved in frozen tissues than in paraffin embedded tissues. In frozen rat tissue, the neuronal nuclei showed a speckled pattern of reactivity, and in many neurons it appeared confined to the nucleoli; in contrast, the cytoplasm reacted in a mild and diffuse, but not granular, pattern. In frozen and paraffin embedded human tissues, the reactivity appeared more concentrated to the nucleoli of neurons, and there was also mild labeling of the cytoplasm. Human and rat systemic tissues, including lung, liver, kidney, spleen, thyroid gland, pancreas, small intestine, colon, heart, skeletal muscle and ovary did not react with anti-Ma IgG, but testicular germ cells, especially spermatocytes and early spermatids, did react. In rat testis, there was speckled staining selectively involving the germ cells of the seminiferous tubule, but no labeling of the Leydig cells in the interstitium was observed. Anti-Ma labeling in human testicular germ cells was restricted to a few dots of nuclear reactivity, with milder, diffuse staining of the nucleus and cytoplasm.

In immunoblots of protein extracts from the same systemic tissues, brain homogenates, and purified neurons (cortical neurons and Purkinje cells), the 4 anti-Ma sera reacted with proteins expressed only in purified neurons and homogenates of brain and testis. In brain, two distinct bands of reactivity were identified at 37 and 40 kDa. In testis, only the 37 kDa protein was found. None of the 337 control sera showed the above immunohistochemical and Western blot reactivities.

-   -   Anti-Ma antibodies specifically recognize paraneoplastic tumors

Paraffin-embedded tumor tissue was obtained from 3 of the 4 patients with anti-Ma antibodies. After tissue deparaffination and antigen retrieval (Cattoretti, G. et al., J. Pathol. 171:83–98 (1993)), all 3 tumors (adenocarcinoma of the breast, adenocarcinoma of the colon and parotid cancer) were found to express antigens identified by anti-Ma IgG antibodies, but in contrast to neurons the reactivity was concentrated in the cytoplasm. Anti-Ma antibodies reacted with the cytoplasm of the tumor cells; no reactivity was identified with normal human IgG antibodies.

The expression of Ma antigens was also examined in frozen or paraffin embedded tumors, including 53 tumors from patients without paraneoplastic syndromes and 13 tumors from patients with other antibody associated paraneoplastic symptoms: none reacted with anti-Ma antibodies.

Initial immunohistochemical findings were reproduced using biotinylated anti-Ma IgG from two different patients, and further confirmed by a competition assay in which preincubation of tissues with any of the anti-Ma sera abrogated the reactivity of the biotinylated IgG from another anti-Ma patient.

C. Cloning and Characterization of the Ma1 Antigen

-   -   Cloning of the Ma1 Antigen

Screening of a λ ZAP human cerebellar library resulted in the isolation of 3 recombinant bacteriophage clones. None reacted with normal human serum. The phage clones were subcloned into pBluescript using the phage excision protocol. The resulting bacterial cDNA plasmids contained inserts of 2139 bp and sequence analysis demonstrated that all clones had identical inserts. Further studies were done using plasmid p8A which was derived from clone 8-3A1.

The cDNA sequence (SEQ ID NO:3, shown in FIG. 1) revealed an open reading frame (ORF) with two putative initiation AUG codons separated by one codon. The first of these, at nucleotide 272, is likely to be the translation initiatior codon as it most closely fits the Kozak consensus rule (Kozak, M., Nucl. Acids Res. 15:8125–8148 (1987)). The ORF extends until the first in-frame stop codon at nucleotide 1258 and encodes a protein of 330 amino acids (SEQ ID NO:4, FIG. 1) with a predicted molecular mass of 36.8 kDa. We called this gene product, Ma1. In addition to the ORF, the cDNA clone includes 5′ non-coding sequence and a 3′ polyadenylation signal (GenBank AF037364, shown in FIG. 1 as SEQ ID NO: 3). A search of the EMBL/GenBank databases revealed that Ma1 cDNA nucleotides 272 to 546 had 97% identity with a human CpG island DNA genomic fragment (GenBank HS19A6R) (Cross, S. H. et al., Nature Genet. 6:236–244 (1994)), and nucleotides 794 to 1230 had 98% homology to cDNA clones derived from a human colon carcinoma cell line (GenBank AA314009) (Adams, M. D. et al., Nature 377:3–174 (1995)) and infant brain (GenBank HO6341). These clones were derived during screenings for CpG islands and expressed sequence tags; no further characterizations have been published. A search of several databases for protein subsequence motifs revealed that the Ma1 protein contains several potential casein kinase II and protein kinase C phosphorylation sites but no other readily identifiable domains.

-   -   Sera from patients with paraneoplastic symptoms recognize Ma1         fusion protein

Using immunoblots of Ma1 fusion protein, the sera of all 4 patients with anti-Ma associated paraneoplastic symptoms reacted with a band of approximately 37 kDa. No reactivity was observed with sham protein (extracts of E. coli with parental plasmid without insert). None of the 337 control sera (patients with cancer but without paraneoplastic neurologic symptoms [cancer of the breast, colon, lung, or testicular germ cells], and patients with paraneoplastic neurologic symptoms [anti-Hu related, anti-Yo related]) reacted with Ma1.

To determine whether the antibodies against Ma1 correspond to the same antibodies that react with brain and testis, sections of these tissues and immunoblots of brain were incubated with anti-Ma sera that had been preabsorbed with Ma1 fusion protein or sham protein. Immunoabsorption with Ma1 protein, but not with sham protein, abrogated all the reactivity with testis and 80% of the reactivity with brain (only a few dot-like reactive granules remained positive in the nuclei of neurons). In addition, the serum preabsorbed with Ma1 no longer reacted with the 37 kDa neuronal protein, but remained reactive with the 40 kDa band, indicating that the 37 kDa protein corresponds to the cloned Ma1.

-   -   Expression of Ma1 mRNA in human tissues

Hybridization of an Ma1 specific oligonucleotide probe to Northern blots of mRNA from multiple human tissues showed that Ma1 mRNA was expressed by brain and testis, but not by placenta, lung, liver, spleen, thymus, prostate, ovary, small intestine, colon or peripheral blood leukocytes. The blots revealed a single band in both brain and testis of approximately 2.6 kilobases. The faint signal observed in heart, skeletal muscle, kidney and pancreas could represent either a very low level of Ma1 mRNA expression, or a trace of nervous tissue contained in these organs. In immunohistochemical and immunoblot assays (see above), these tissues did not react with anti-Ma serum, indicating no Ma1 protein expression.

Example 2 Identification of Cancer-Brain Antigen Using Serum Antibodies from Patients with Testicular Tumors and Paraneoplastic Limbic and Brainstem Encephalitis

A. Materials and Methods

-   -   Sera and tissues         The sera (or CSF when available) of 986 patients with         histologically proven cancer that were sent to us for         antineuronal antibody testing were used in the study. A total of         304 sera were used as controls; these controls included patients         with cancer and paraneoplastic syndromes (45 PLE and tumors         other than testicular cancer [13 anti-Hu positive]; 23 anti-Hu         positive encephalomyelitis-sensory neuronopathy; 20 anti-Yo         associated cerebellar degeneration; 5 Lambert-Eaton myasthenic         syndrome, all positive for P/Q-type VGCC antibodies; 6 anti-Ri         associated cerebellar ataxia and opsoclonus; and 9 myasthenia         gravis and thymoma), patients with cancer but without         paraneoplastic syndromes (44 testicular cancer; 10 colon cancer;         10 ovarian cancer; 21 breast cancer), and patients with         miscellaneous disorders (41 multiple sclerosis; 35 systemic         lupus erythematosus), and 24 normal individuals. All sera were         kept frozen at −70° C.

Tumor tissues were provided by the referring physicians and by the Tumor Procurement Service at Memorial Sloan-Kettering Cancer Center. They included: 4 testicular tumors from patients with PLE-BE; 45 from patients without paraneoplastic syndromes (25 testicular germ cell tumors, 5 colon, 4 breast, 3 lung, 2 parotid gland and 6 SCLC), and 8 from patients with other paraneoplastic syndromes (4 SCLC, 3 ovary, 1 bladder). Normal human tissues and Wistar rats tissues were obtained as reported (Dalmau, J. et al., Am. J. Pathol. 141:881–6 (1992)), and kept at −70° C. Other samples from the same tissues were embedded in “Optimal Cutting Temperature” medium (OCT, Miles Inc, USA) and snap frozen in isopentane chilled by liquid nitrogen.

For Western blot analysis, tissues were homogenized in 0.1% Nonidet P-40 and protease inhibitors, as reported (Dalmau, J. et al., Am. J. Pathol. 141:881–6 (1992)).

-   -   Immunohistochemistry

Seven micron-thick frozen sections of rat and human tissues were fixed in 10% formalin, 100% methanol, or cold acetone (4° C.), and incubated with the patient's serum, IgG, or CSF using immunohistochemical methods previously reported (Dalmau, J. et al., Am. J. Pathol. 141:881–6 (1992)).

To avoid reactivity with endogenous IgG, all immunohistochemical studies with human tissues utilized IgG purified from patients' sera and labeled with biotin. The same IgG was used for immune competition assays: two sera were considered as competing for the same epitopes when preincubation of the tissue with one serum abrogated the reactivity of the other serum's IgG.

-   -   Intrathecal Synthesis of Ta antibodies

Intrathecal synthesis of Ta antibodies was calculated by the Schüller's formula (Schuuler, E., in Trends in Neuroimmunology (Marrosu, M. G., Cianchetti, C., and Tabolato, B., eds), Plenum Press, New York, 1990, pp. 3–12). A ratio of intrathecal antibody specific activity (ASA)/serum ASA>2 was considered a positive intrathecal synthesis.

-   -   Cloning, Isolation and Sequence Analysis of Ma2 cDNA

Using the serum of a patient with paraneoplastic brainstem dysfunction, a λ ZAP human cerebellar library (Stratagene, La Jolla, Calif.) was screened at a density of 5×104 pfu/150 mm plate. After 4hours of growth at 42° C. plaques were overlaid with nitrocellulose filters soaked in 10 mM isopropyl b-D-thiogalactopyranoside (IPTG) and incubated for 12 hours at 37° C. Filters were removed, blocked with 1% bovine serum albumin in phosphate buffered saline (PBS), and incubated with the patient's serum (diluted 1:1000) for 2 hours at room temperature. Positive phage colonies were identified and purified by several rounds of antibody screening, followed by subcloning into pBluescript using the in vivo excision phage rescue protocol (Stratagene).

Double-stranded Ma2 cDNA was purified using the Qiagen plasmid midi-prep system (Qiagen, Santa Clarita, Calif.) and sequenced on both strands. Sequence analysis using internal oligonucleotide primers, as well as SK and KS primers was performed with an automated DNA sequencer (Applied Biosystems , model 377) using the dye terminator fluorescence method (Lee, L. G. et al., Nucl. Acids Res. 20:2471–2483 (1992)).

-   -   Western blot analysis

Fusion protein, E. coli protein, and proteins from human and rat tissues were obtained as previously described (Dalmau, J. et al., Am. J. Pathol. 141:881–6 (1992); Manley, G. T. et al., Ann. Neurol. 38:102–110 (1995)), resolved by 10% SDS-polyacrylamide gel electrophoresis, and transferred to nitrocellulose. Nitrocellulose strips were then incubated with the patients sera (diluted 1:1,000) and the reactivity demonstrated by an enhanced chemiluminescence method (Amersham, Arlington, Ill.).

-   -   Northern blot analysis

Sequence specific oligonucleotide probes were end-labeled with [g-³²P] ATP using T4 polynucleotide kinase, and purified over a G-25 sephadex column. As probe for Ma2, the following oligonucleotide was used: 5′-GGGAATGGCCGAGACATC-3′ (SEQ ID NO:5) (cDNA base pairs 234–217), and as probe for β-actin, the following oligonucleotide was used: 5′-GTCTTTGCGGATGTCCACG-3′ (SEQ ID NO:2). Probes (1×10⁷ cpm/mL) were hybridized to “Human Multiple Tissue Northern Blots I and II” (Clontech, Palo Alto, Calif.) overnight at 42° C. in Rapid Hyb buffer (Amersham). Blots were washed for 15 minutes at RT in 5×SSC (20×=NaCl 3M and Na₃Citrate 0.3M, pH 7.0), 0.1% SDS; at 42° C. in 1×SSC, 0.1% SDS; and at 42° C. in 0.1×SSC, 0.1% SDS. After hybridization with the Ma2 probe, blots were stripped by boiling in 0.5% SDS for 10 minutes and hybridized with β-actin probe. For visualization, blots were exposed to XAR film for 72 hours at −80° C.

B. Results

-   -   Patients

Among 986 patients with several types of cancer whose sera were examined for onconeuronal antibodies, 20 had testicular cancer and diverse paraneoplastic syndromes. Ten of these 20 patients harbored similar antineuronal antibodies, termed Ta (see below), and all 10 suffered from PLE, BE, or both (Table 2). Only 1 of 9 patients with PLE did not harbor Ta antibodies.

TABLE 2 Paraneoplastic Symptoms in 20 Patients with Testicular Cancer Ta Ta antibodies (+) antibodies (−) Limbic encephalitis* 8 1 Brainstem** 2 2 Cerebellum 0 1 Basal ganglia dysfunction 0 1 Sensory neuropathy 0 3 Optic neuritis-myelitis 0 1 Motor neuron syndrome 0 1 (*)Two (2) patients also had brainstem dysfunction, and another 2 had severe hypothalamic involvement. (**)Prominent brainstem dysfunction.

The clinical features of the patients with Ta antibodies are shown in Table 3. Eight patients had PLE (2 associated with BE); symptoms included, severe memory loss (n=5 patients), seizures (n=6), and hypothalamic-diencephalic dysfunction (2 hyperthermia, 1 hypersomnia, 1 pathological increase of weight, 1 pituitary hormonal deficits). Two additional patients had prominent BE with marked eye movement abnormalities. Mild cerebellar symptoms were identified in 3 patients, all with conspicuous signs of BE.

TABLE 3 Clinical Features of 10 Patients with Paraneoplastic Symptoms Associated with Ta Antibodies CNS Diagnostic Tumor Tumor # Sex Age First Symptoms Syndrome Tests Diagnosis Type Treatment Status  1 M 28 Resting tremor, slow Basal ganglia, CT: normal 1 year prior to NSGCT orchiectomy, plasma Neurology: stable mentation, anxiety, PLE *CSF: abnormal the ND exchange, Tumor: NED (3 irritability, corticosteroids years) depression, dystonia, seizures, memory problems  2 M 45 Depression, memory PLE **MRI: abnormal 3 years after NSGCT orchiectomy, Neurology stable; changes, seizures, CSF: normal the ND chemotherapy Tumor: NED (9 weight gain (20 lbs) Brain biopsy: years) PLE  3 M 26 Memory loss, PLE MRI: abnormal 9 months after NSGCT orchiectomy, Neurology: seizures CSF: abnormal the ND chemotherapy remission; Brain biopsy: Tumor: PLE NED (3 years)  4 M 37 Severe memory loss, PLE, BE MRI: abnormal 2 months after Seminoma orchiectomy, Neurology: mild brainstem signs, CSF: abnormal the ND chemotherapy, remission; hypersomnia ccorticosteroids Tumor: metastases  5 M 22 Seizures (left facial PLE MRI: abnormal 6 months after MGCT orchiectomy, Died of twitching and CSF: abnormal, the ND chemotherapy, neurological abnormal taste in Brain biopsy: carbamazepine deterioration mouth) PLE  6 M 28 Hallucinations, PLE, cerebellar MRI: abnormal 6 months after MGCT orchiectomy, Died of seizures (dejà vu), CSF: abnormal the ND chemotherapy complications of memory loss, chemotherapy hyperthermia  7 M 45 Ataxia, dysarthria BE, cerebellar MRI: normal 6 months after Seminoma orchiectomy, Neurology: partial CSF: normal the ND radiation, improvement carbamazepine Tumor: NED (3 years)  8 M 28 Visual/auditory PLE, BE MRI: abnormal 7 months prior NSGCT orchiectomy, Neurology: hallucinations, CSF: abnormal to the ND steroids, IV Ig deterioration; confusion, eye Brain biopsy: Tumor: NED (9 motility disfunction, PLE months) memory loss, hyperthermia  9 M 32 Diplopia, dysarthria, BE, cerebellar MRI: normal 12 months after Seminoma orchiectomy Neurology: stable oscillopsia CSF: normal the ND Tumor: NED (4 months) 10 M 38 Lethargy, loss of PLE, MRI: abnormal 5 months after Seminoma orchiectomy, Neurology: mild libido, diabetes diencephalon, CSF: abnormal. the ND dexamphetamine, improvement insipidus, hypothalamus IV Ig, Tumor: NED (3 hypothyroidism, corticosteroids months) urinary incontinence, mutism, hypersomnia, Decreased voluntary movements. ND: Neurologic disease; NSGCT: Non-seminomatous germ-cell tumor; MGCT: mixed germ-cell tumor; PLE: paraneoplastic limbic encephalitis; BE brainstem encephalitis; IV Ig: Intravenous immunoglobulin; NED: no evidence of disease (cancer). (*)CSF: abnormal, indicates elevated proteins, pleocytosis, or both. In all patients, the CSF cytology was negative for cancer cells (**): MRI of the head: abnormalities on T2-weighted sequences involving one or both temporal lobes (n = 7), suprasellar-diencephalic regio (n = 3), and uptake of gadolinium in temporal or diencephalic regions (n = 3).

Neurological symptoms developed before the tumor diagnosis in 8 patients (median 6 months, range 2–36 months); in the other 2 the tumor diagnosis preceded the neurological disorder (7 and 12 months). Head MRI was abnormal in 7 PLE patients; the typical findings included a bright signal in the medial aspect of the temporal loves, and sometimes the diencephalon. Four patients underwent brain biopsy; all showed inflammatory infiltrates, gliosis, and neuronal degeneration. More intense signal in a right temporal lobe corresponded to local edema after a brain biopsy, which showed perivascular inflammatory infiltrates and multiple perineuronal infiltrates of T cells Two patients had relapsing and remitting neurological symptoms: one was reported elsewhere (Burton, G. V. et al., Cancer 62:2248–2251 (1988)), the other had symptoms for 12 months until the detection of serum Ta antibodies established the diagnosis of paraneoplastic BE and lead to the discovery of the tumor. All patients had testicular tumors (4 seminomas and 6 non-seminomatous germ cell tumors). At the time of tumor diagnosis, 4 patients had systemic metastasis.

All 10 patients underwent orchiectomy, 5 received chemotherapy, and 1 radiation therapy. The neurologic disease was treated with steroids (n=4), plasma exchange (n=2), and intravenous immunoglobulin (IVIG, n=1). Only one patient treated with IVIG and steroids improved. Overall, 5 patients improved neurologically (2 with total remission), 2 remained stable, 1 deteriorated, and 2 are dead (one from complications of chemotherapy; the other from the neurologic disease).

-   -   Detection of Ta antibodies

Using immunoblots of purified human neurons, the sera of the 10 patients (and CSF available from 6) reacted with a 40 kDa protein. The distribution and pattern of reactivity was examined by immunohistochemistry of human and rat tissues using several fixatives and different tissue processing. All sera and CSF showed a similar brain-specific reactivity. The most intense immunolabeling was obtained with frozen tissue and acetone or methanol-acetone fixation. Using these conditions most neurons of the central nervous system showed discrete subnuclear and cytoplasmic reactive structures; the reactivity appeared concentrated in the nucleoli and perikaryon. With formalin fixed tissue, only subgroups of neurons of the amygdaloid complex, large neurons of the brainstem, and the dentate nucleus of the cerebellum remained positive. Preincubation of tissues with any of 8 sera abolished the reactivity of the IgG isolated from the other 2 sera, suggesting that all sera had similar epitope specificity.

The reactivity defined by these immunoblot and immunohistochemical techniques was called “Ta” (after the first two letters of the index patient's name). Ta antibodies were not identified in 304 control sera, including patients with cancer and paraneoplastic syndromes (45 PLE and tumors other than testicular cancer [13 anti-Hu positive]; 23 anti-Hu positive encephalomyelitis-sensory neuronopathy; 20 anti-Yo associated cerebellar degeneration; 5 Lambert-Eaton myasthenic syndrome, all positive for P/Q-type VGCC antibodies; 6 anti-Ri associated cerebellar ataxia and opsoclonus; and 9 myasthenia gravis and thymoma), patients with cancer but without paraneoplastic syndromes (44 testicular cancer; 10 colon cancer; 10 ovarian cancer; 21 breast cancer), and patients with miscellaneous disorders (41 multiple sclerosis; 35 systemic lupus erythematosus), and 24 normal individuals (anti-Hu: see Szabo, A. et al., Cell 67:325–333 (1991); anti-Yo: see Peterson, K. et al., Neurology 42:1931–37 (1992); anti-Ri: see Luque, F. A. et al., Ann. Neurol. 29:241–251 (1991)).

C. Cloning and Characterization of Ma2, the Antigen Recognized by Ta Antibodies

-   -   Cloning of Ma2

The screening of a λ ZAP human cerebellar library with the serum of a patient resulted in the isolation of a positive clone, which was recovered by subcloning in pBluescript. The resulting plasmid (p561A) contained an insert of 614 bp. Sequence analysis revealed the presence of an incomplete open reading frame of 195 amino acids, with a predicted molecular mass of 21.9 kDa (GenBank AF037365, shown in FIG. 2 as SEQ ID NO:6). The nucleic acid sequence (SEQ ID NO:6) and predicted amino acid sequence (SEQ ID NO:7) are shown in FIG. 2. A stop codon at 586 bp is almost immediately followed by an apparent polyadenylation signal. The methionines at amino acids 12 and 21 do not closely fit the Kozak consensus rule for initiation codons making it unlikely that the clone is complete at the 5′ end. The protein expressed by this cDNA was called, Ma2.

It was found that the cDNA sequence of Ma2 is partially homologous to Ma1 (FIGS. 3A and 3B), the paraneoplastic antigen expressed in brain and testis (see Example 1). A search of the GenBank databases revealed that the Ma2 cDNA had 84% homology to a human cDNA clone derived from RNA extracted from demyelinating lesions of a patient with multiple sclerosis (GenBank N47784). Further analysis showed that the area of highest homology (95%) is within the putative protein coding region of Ma2 and in fact, accounting for sequencing errors, the 2 clones are likely identical in this region. The N47784 clone has a potential ORF that extends beyond the Ma2 stop codon. In addition, Ma2 was found to have 60% homology to a cDNA clone isolated from adult mouse testis (GenBank 918103).

-   -   Patients with testicular cancer and PLE-BE harbor serum         antibodies against Ma2 and have an intrathecal synthesis of         these antibodies

Using immunoblots of Ma2 fusion protein, all sera and CSF from patients with Ta antibodies reacted with a band of approximately 32 kDa. No reactivity was obtained with immunoblots of sham protein (E. coli with parental plasmid without insert). None of 304 control sera reacted with Ma2.

To determine whether Ma2 corresponds to the 40 kDa neuronal protein identified by Ta antibodies, immunoblots of neuronal proteins were incubated with anti-Ta sera preabsorbed with Ma2. Preabsorption with Ma2, but not with sham protein, abrogated the serum reactivity with the 40 kDa neuronal protein, suggesting that this protein is Ma2. The ratio of intrathecal ASA/serum ASA of Ta antibodies was 0.74, 4.4, 6.2, 16.9, and 23.5, consistent with a positive intrathecal synthesis (>2) in 4 of 5 patients.

-   -   Ma2 is expressed by normal brain and by the tumor of patients         with PLE-BE

Northern blot analysis of mRNA extracted from multiple human tissues showed that Ma2 mRNA is expressed by brain, but not by placenta, lung, liver, spleen, thymus, prostate, ovary, testis, small intestine, colon or peripheral blood leukocytes. The Northern blots revealed a single transcript expressed in brain of approximately 6,500 kilobases. Immunohistochemical and Western blot analysis of the same tissues, using biotinylated anti-Ta IgG as a probe, showed that only brain expresses Ma2 reactivity.

The tumors of 4 patients with PLE-BE and Ta antibodies were available in formalin-fixed, paraffin-embedded blocks. After tissue deparaffination and antigen retrieval, all 4 tumors showed reactivity with anti-Ta IgG. No reactivity was observed when the IgG had been preabsorbed with Ma2 protein. Results were similar with sections or fat hippocampus. No Ma2 reactivity was expressed by 53 diverse tumors (including 25 testicular cancers) from patients without paraneoplastic syndromes or with other paraneoplastic disorders.

D. Ma1 and Ma2 are targets of immunological responses associated with different profiles of neurologic symptoms and tumors

Because of the sequence homology between Ma1 and Ma2, it was examined whether anti-Ta and anti-Ma sera react with both proteins. These studies showed that all anti-Ta sera react exclusively with Ma2, but the anti-Ma sera recognize both Ma proteins. Preabsorption of anti-Ma sera with any of these proteins did not abrogate the reactivity with the other one, indicating that the epitopes in Ma1 and Ma2 are different. In addition, preincubation of rat brain sections and immunoblots of neuronal proteins and Ma2 with any anti-Ma serum decreased, but did not abolish, the reactivity with anti-Ta IgG suggesting that some, but not all, Ma2 epitopes are recognized by both types of sera. The clinical-immunological associations derived from these studies are summarized in FIG. 4.

Example 3 Identification of Ma3, Ma4 and Ma5

Screening of a human brainstem cDNA library, using the same techniques as described above for isolation of Ma1 and Ma2 from the cerebellar library, resulted in the isolation of 3 additional clones with homology to Ma3 and Ma2; these were named Ma3, Ma4 and Ma5. Ma3 is 833 nucleotides long, encoding a fusion protein of 21 kilodaltons. Ma4 is 1574 nucleotides long, encoding a fusion protein of 36 kilodaltons. Ma5 is 2248 nucleotides long, encoding a fusion protein of 56 kilodaltons. The fusion proteins are those proteins expressed by the cDNA clones in pBluescript, which is a fusion between the clone and the 5′-end of the β-galactosidase gene. The cDNA for Ma3, Ma4 and Ma5 have been deposited in Genbank as AF083114 (Ma3, shown in FIG. 5 as SEQ ID NO:8), AF083115 (Ma4, shown in FIGS. 6A–6B as SEQ ID NO:10), and AF083116 (Ma5, shown in FIGS. 7A–7B as SEQ ID NO:12). The putative encoded polypeptides for Ma3, Ma4 and Ma5 are shown in FIGS. 5 (SEQ ID NO:9), 6A–6B (SEQ ID NO:11) and 7A–7B (SEQ ID NO:13), respectively.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 

1. An isolated Ma family polypeptide comprising an amino acid sequence selected from the group consisting of: SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, and SEQ ID NO:13.
 2. An isolated fusion protein comprising a Ma family polypeptide, wherein the Ma family polypeptide comprises an amino acid sequence selected from the group consisting of: : SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, and SEQ ID NO:13. 